They call it the zud, a prolonged period of heavy snows and paralysing cold that adds to the challenges of living on a treeless expanse nearly the size of Alaska. Mongolia and its 800,000 herders are reeling from the worst winter that anyone can remember. According to United Nations relief officials, nearly eight million cows, yaks, camels, horses, goats and sheep died, about 17% of the country's livestock. Even if the spring rains arrive soon, 500,000 more animals are expected to succumb.

"This is not only a catastrophe for the herders but for the entire Mongolian economy," said Akbar Usmani, of the United Nations Development Programme. "We expect the ripple effects for months and years to come."

The last serious zuds, three consecutive harsh winters between 1999 and 2002, sent thousands of destitute nomads streaming into the capital, Ulan Bator. A decade later, their tattered yurts still crowd bleak neighbourhoods on the city's fringe as the former herders struggle to fit into the modern world. The UN estimates the current disaster may prompt as many as 20,000 herders to abandon their nomadic life and flee to the city. "A lot of the herders have no skills so they usually end up breaking the law and falling into poverty," said Buyanbadrakh, the governor of a small administrative district known as a soum, who, like some Mongolians, uses a single name. He said 70% of the livestock in his soum, Zuunbayan-Ulaan, was wiped out this year, with at least 2,800 families losing their entire herds.

The disaster poses a challenge to a government already struggling to address the needs of the third of the population that lives in poverty. But it also raises questions about climate change, environmental degradation and whether the pastoral way of life that sustains many of the country's three million people has a future. Although mining and tourism are a growing portion of the Mongolian economy, a third of the population still depends entirely on husbandry for its livelihood. "The key question we have to ask is whether this way of life is sustainable," said the UN's Usmani. "It's a very sensitive issue."